Blood bird's nest:

Jin Siyan species of Swift uses saliva to build nests and lay eggs, which is rare in yield and high in nutritional value. It has been a valuable tonic since ancient times. Because it is a periodic physiological reaction for Jin Siyan to secrete saliva before laying eggs, there is no difference in the quality of bird's nest picked three times a year. Swallows that draw blood are mostly produced in Luolanyan Mountain, Kangshi Mountain, Songkhla Mountain and other places in Thailand, and are not formed by the legendary swallows vomiting blood. Data show that the quality of blood swallow is actually better than that of white swallow, and the aroma and components obtained by soaking are not as good as those of Bai Yan. Blood swallows have become more and more valuable in recent years.

Blood bird's nest picture: